Brent Sordyl's blog

1. Response speed should be of utmost importance.
2. More space comes in at a close second to speed.
3. Intuitiveness of your design also becomes a heightened concern.
4. Ambidextrous design must come into consideration in the touch screen world.
5. Bright background colors or patterns can hide glare and reduce fingerprints.
6. Touch screen interfaces are more suited to information retrieval than data entry.
7. Be aware of screen coverage.
8. Problems with eye-finger and eye-stylus parallaxes lend even more credence to the argument for big, fat areas to press with plenty of space between them.Best to worst operations: Point, select > Position, orient (rotate), define path > Enter values > Enter text.

So, basically, touch screen interface’s are great for data retrieval, pretty good for data manipulation, and are kinda awful for data entry.

(Full Story: Best Practices of Touch Screen Interface Design)